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Situation : I have a Beowulf cluster with two compute node say node-1[192.168.2.10] and node-2[192.168.2.11]. Among them node-1 is acting as nfs server – providing common home directory for both the compute node. The NIS server is also on node-1 allowing uniform login and authentication on all compute node.

Both the compute node are connected to each other with Gigabit Ethernet switch. This is how my Beowulf cluster is organized. I have installed OpenMPI-1.4.3 on on both node at /usr/local location. Environment variables are properly set in .bashrc file of the common login ID in cluster for runtime linking and loading of libraries.

where both the system[ node-1, node-2] is dual socket quad core system.

For simple testing purpose while I run a simple hello world program using following command

mpiexec -np 16 -hostfile hostfile.txt ./helloWorldMPI

it runs perfectly. But while I run HPL with following command

mpiexec -np 16 -hostfile hostfile.txt ./xhpl

It simply stalls. Which means I can see 34% to 40% use of each of the core on each of the system [ using top command ] – but it continues that way and no output comes ever on screen – that is too even for small problem size say N=200 . It run forever till I feel like killing the job.

But instead of using OpenMPI if I use MPICH-2 with same system configuration to run HPL, then computation completes – output comes in perfect form.

Solution : As usual I have gone through lot of materials and forums related to OpenMPI and HPL. Some of them are listed bellow. One of them talks about HPL_NO_MPI_DATATYPE [ see the thread ]

I have tried this , with no help. After a lot of trial-and-error, I zeroed in at conclusion that as each of the compute node of my cluster is having multiple Ethernet connectivity port [ eth0,eth1,eth2 ] , the OpenMPI is confused at the time of HPL-MPI communication[ send/receive ] about – which port to use for packet transfer. This understanding takes me to Mailing List Archives which talks about MCA flag “btl_tcp_if_include eth0”. So I decided to give it a try – and surprisngly this solved my problem. The final command is as follows

AHH …..Ah….what a relief … thank God .. after such long irritating trial-and-error – I am relaxed now :D. As I found almost no citation of this issue on web I decided to write it down for us. I hope this will help Others too…

Its been 42 years , India is starving for a bill like Lokpal BIll. Now when Anna Hazare fights for it , spineless politicians of our country says its a premature step toward bringing this bill to country.

SHAME ON THEIR ATTITUDE.

I believe this time it is not fight between corruption and people at first step. Actually this is fight between a creature called Politicians and fearless people of our country.

I am waiting for JASMIN REVOLUTION against politicians In India this time.

[ Note – 1) consider all politician in same category. all of them did nothing – in order to keep them immune from accountability.
2) Even after 40 years if politicians says “we need to discuss” , “we are in the process” , “we have taken numerous steps towards it” — It proves that they are lying – hence they are lairs as they were. ]

I was trying to install latest version of qt on CentOS 5.4 , It went smooth. But at the end of installation there was a message saying that all the application may not run because of some library dependency. I ignored that message and decided to proceed. But unfortunately when I try to lunch qt creator from shell , it failed because of libstdc++ library dependency with following message.

I explored and found that my system is having libstdc++.so.6.0.8 which comes with base compiler of the system [ i.e. gcc 4.1.2] and it does not contain the symbol “GLIBCXX_3.4.9”.

$ readelf -s libstdc++.so.6.0.8 | grep GLIBCXX_3.4.9[ no output ]

Solution : Installing more latest version libstdc++ [ libstdc++.so.6.0.9 ] is the perfect solution, but I choose to install the gcc4.4.0 at /usr/local location and link the binary with the library libstdc++.so.6.11 with qt – which contain the symbol

Road to Sinhgad, a favorite week end picnic spot for puneties [ people form pune, india] is closed for development work. I visited the place yesterday , 13th Feb. But I could not take the vehicle road to reach hill top. I had to take the trekking road. It took me two and half hour to reach at top from base by walk/ trekking.

I would suggest people who are going to visit Sinhgad through car route, please postponed your trip for 3 month.

In the mean time if you are interested to trek to top then opt for morning slot because at noon , trekking will be very tough.

There is direct PMPL Buses to Sinhgad from Saniwarwada , pune at morning time.